Ni diffusion in vertical growth of MoS2 nanosheets on carbon nanotubes towards highly efficient hydrogen evolution

The effect of transition metal particle size and distribution on the catalytic performances of carbon nanotubes (CNTs)-based catalysts has been attracting considerable attention in recent years. In this paper, Ni nanoparticles with a Ni 3 C shell structure were embedded in N-doped CNTs by thermal condensation of dicyandiamide with Ni salts followed by MoS 2 nanosheets deposition. Most interesting, dissolution, redistribution and diffusion of the embedded Ni/Ni 3 C nanoparticles take place during the stage of deposition of MoS 2 nanosheets on the CNTs with the help of excess S precursors. The dissolution, redistribution and diffusion result in the disappearance of Ni nanoparticles and formation of much finer Ni nanoclusters , which significantly facilitates the deposition and formation of vertical MoS 2 nanosheets on CNTs. The homogeneous distribution of Ni nanocluster leads to improved intrinsic conductivity and increased active sites. N-doped CNTs with optimized Ni and MoS 2 loading revealed high activity and stability for electrocatalytic hydrogen evolution reaction (HER). The as-prepared MoNiCNTs electrocatalysts exhibit superior HER activity with low onset potential and small Tafel slope value in both acidic and alkaline electrolyte conditions. The result provides a new platform for rational design and fabrication of high-performance non-precious transition metal based HER electrocatalysts.